Tanks or other containers are used in many situations to store resources, such as liquids, for use or re-use. Equipment or machines which use liquids may require different amounts of liquid at different points in time, which makes the storing of these liquids an important piece of said equipment or machine. These liquids could be used to perform various functions depending on the equipment or machine and the liquid itself, such as cooling, hydraulics, lubrication, measuring or being expelled or taken in.
One specific example employment for storage tanks is use as expansion tanks. An expansion tank is a storage tank which is adapted to compensate for thermal expansion of the liquid in a liquid system. If the temperature of the liquid in the liquid system increases, the liquid thus has room to expand without damaging the equipment of the liquid system, and sufficient liquid is available in the liquid system also during very cold operating conditions.
In order for proper functioning of the expansion tank, the tank must therefore not be completely filled at temperature operating point below a maximal temperature operating point. Instead, a preferred fill level of the tank must be carefully selected taking into account the temperature of the liquid at time of filling, the expansion volume needed for the liquid in the liquid system when operating at a maximal operating temperature, the liquid volume needed for compensating for liquid contraction when operating at a minimum operating temperature, and possibly also a certain liquid reserve volume for compensating for a certain loss of liquid from the system over time.
Filling of prior art storage tanks is for example performed manually or automated by filling the storage tank with a predetermined amount of liquid, or filling the storage until the fill level equals a predetermined fill level. While these solutions work well in some situations, there is still room for improvements in terms of filling of storage tanks.